Boss CS 1 LED won't stay lit

[BDuguay]

So, I have a functioning Boss CS 1 but, when engaged, the effect works but the LED won't stay on. This is both with a fresh battery and PSA 120 adapter.
What should I be looking for?
TIA,
B.

[Mark Hammer]

Hi Brian,

Is it only the LED or is the bypass switching also unstable?

[Groovenut]

Is this a very old CS-1?

IIRC, the originals only had a battery check LED that didn't stay on when the effect was on.

Just a thought.

As Mark asked, does the pedal function properly otherwise?

[BDuguay]

The bypass switching works fine. It's just that when the pedal is engaged, the LED does stay on. If I hold the switch down the LED stays on but once the switch is released, it turns off. This is an early silver screw version.
Thanks fine people.

[BDuguay]

I realized I mis-typed. The LED does not stay on when the pedal is engaged, even though the effect itself works. Who here knows about the circuit involved in Boss  pedal switching?
As always, thanks for your replies.
B.

[antonis]

Who here knows about the circuit involved in Boss  pedal switching?

The JFET Bypass is made of one switch Q9 and a toggle block formed by Q6 and Q7 to manage the switch. This configuration can activate/deactivate the effect using a simple push button.



The JFET Bypass Switch enables two possible toggle configurations:

It can turn the effect on, activating the Q9 BJT and allowing the wet signal to be taken into consideration by the output stage summing amplifier.
It can turn the effect off, deactivating the Q9 BJT and isolating the wet signal from the summing amplifier.
The Boss/Roland pedals have similar switching setup to the Ibanez/Maxon. For a detailed information check the Tube Screamer Switching Circuit.
https://www.electrosmash.com/tube-screamer-analysis

[ElectricDruid]

Is this a very old CS-1?

IIRC, the originals only had a battery check LED that didn't stay on when the effect was on.

There's other mentions of this around the web. It makes sense on an early pedal, since they were intended for battery use and LEDs back then drew 20mA, which is enough to eat you Everready PP3 in short order.

I think what you're seeing is a design feature. One that doesn't make much sense in the 21st century, but which made lots of sense in the 1970s.

[duck_arse]

https://www.tonehome.de/app/download/8819857/Boss_CS1_servicemanual.jpg

linked img shows bottom right corner, the footswitch directly operates the indicator led, only when depressed.